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  #1  
Old 03-30-2004, 01:27 AM
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Amp turns on but no sound

I wired my factory head unit speaker leads to an MTX 404 4ch amp high level input. The amp turns on when I start the vehicle - the LED is on, but no sound when I put a CD on. I have a seperate amp driving a sub chained to the 4ch amp. The sub thumps once to start and then nothing. I fiddled with the inputs, switching the 4 ch amp input to the sub input to see maybe that the 4ch amp was defective and the sub worked. And when I changed everything back the 4ch came on. But shut the vehicle down and next time power on the amp LED's come on but no sound. Anyone have any ideas?

By the way, Factory head unit is premium sound single CD
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  #2  
Old 03-30-2004, 01:33 AM
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Well i dont exactly know the answer to your question but EVERY single time I helped install subwooferes with a stock head unit, I/we used line level converters.(I worked with a buddy who owns a stereo shop)
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Old 03-30-2004, 03:46 AM
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Quote:
Originally posted by sk8inrj1
Well i dont exactly know the answer to your question but EVERY single time I helped install subwooferes with a stock head unit, I/we used line level converters.(I worked with a buddy who owns a stereo shop)
Said he connected them to the high level inputs so he does not need one, basically the amp has one built in.

My guess would be that you have the amp wired wrong as far as signal wires go...
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  #4  
Old 03-30-2004, 09:38 AM
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Where did you tap into the speaker leads at and did you use the existing (OEM) speaker leads off the amp into the door speakers? Are we sure this thing doesn't have an external amp anywhere from the factory?
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Old 03-30-2004, 04:13 PM
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Sticker,

Thanks for the reply. I ran from speaker lines at back of radio to amp. Then from amp back to vehicle harness.

I put a multimeter on the high level amp input and got about 1.8 volts - seems low. So I might have a factory amp somewhere down the vehicle harness. But I thought the amps weren't used after 1998. If I have a factory amp what would it look like and where would it be?
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  #6  
Old 03-30-2004, 04:30 PM
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How high was the volume when you got 1.8? Was it still hooked up to the amp when you tested it?

I did not see your sig before I asked the question. I am pretty sure you do not have an amp though with a 2002. Anyone else know this for a fact?

Things to check

Is it the power led that is on or is it a protection light?

Test all your power leads using the ground you have the amp on. Touch the ground of your MM to the top of the ground bolt. What voltage are you seeing at the main power? What are you seeing at the turn on lead? Does the multimeter act weird jumping around when testing using the top of the bolt for the ground?

Double then triple check the high output wires you have feeding the amp. Did you get a wire adapter or cut the plug? I'm asking this to make sure the speaker leads are marked, otherwise you very well could have a lead wrong.

Does the sub play if you bypass feeding the MTX amp? Is the MTX amp new? If not, have you listened to that amp in another vehicle?

Sorry for all the q's, just trying to help you diagnose this thing.
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  #7  
Old 03-30-2004, 11:08 PM
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Sticker, answers to questions:

Volume at 1.8 was fairly loud

The led is a power on indicator, off for fault, overheat, etc

Main power voltage is 14.1, no power on lead at the 404. It detects high level and turns on.

The high output wires are crimped into adapter leads. I didn't cut vehicle wires. Easier to return to stock.

The MTX 404 is new.

And, yes, the sub plays, via high level when I bypass.

So, looks like next step is to return the 404 and try a replacement.

Thanks for your help.
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  #8  
Old 03-30-2004, 11:35 PM
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Weired! If you can, take it back!

Let us know if the new one works out for you. Otherwise it's in the install.
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  #9  
Old 03-31-2004, 12:08 AM
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Its actually your head unit that has gone into "protection". MTX knows about this problem with the Fords, and they responded to my same problem with this reply.

"We know of the problem, its the head unit going into protection, due to the feedback from the amp on turn on. Only way to get around this is hook the amp turn on lead to a keyed power source"

So hook up the amp turn on lead to a power lead that is on when the key is turned on. I have the same setup in my truck, and have gotten around it by remote starting my truck. Doing this turns the amp on before the stereo is on, and it works fine, but if I start it with the key, I get no sound. I am going to rewire it when I get a chance. Hope this helped you.

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  #10  
Old 04-13-2004, 01:16 AM
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Haku,

Thank you for your reply, you read my situation very accurately. I did not return the amp. It was fine. The problem is the high level input of the MTX combined with the Visteon head unit. Rather than trying to figure out how to power the amp before the head unit I installed one of David Navone's LOC's. Problem solved. I went on, installed new door speakers, and a little Dynamat. Pretty good sound now. Thanks again.
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Old 04-13-2004, 01:16 AM


 
 
 
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